It was back in September that Green Day singer Billie Joe Armstrong went to rehab, but nobody really knew why he was there. Well, we knew his onstage "I'm not f*cking Justin Bieber, you motherf*ckers" meltdown was the tipping point, but we didn't know anything specific about his addiction. But we'll have plenty of details when the new issue of Rolling Stonehits newsstands with the exclusive cover story "Billie Joe: The Road Back from Hell," in which the frontman opens up about his "years of alcohol and prescription drug abuse."

No word yet on which prescription drugs were the problem, but this still comes as a surprise to some -- after all, it was kind of a big deal when Billie Joe gave up getting stoned (if you've ever listened to any early Green Day lyrics, you understand why). But his experience just serves as yet another example of the dangers of "legal" drugs, particularly when combined with alchohol. Seriously, things were NOT good ...

"I couldn't predict where I was going to end up at the end of the night," he says in the Rolling Stone article. "I'd wake up in a strange house on a couch. I wouldn't remember how. It was a complete blackout."

And of the Justin Bieber-themed rant in Vegas:

"I remember tiny things. The next morning, I woke up. I asked [my wife] Adrienne, 'How bad was it?' She said, 'It's bad.' I called my manager. He said, 'You're getting on a plane, going back to Oakland, and going into rehab immediately.'"

Seems like that was the best decision he could have made, as things are going much better these days (Green Day will resume touring in March). Hopefully this time Billie Joe will have all the support he needs to make it through.